U.S. patent number 9,459,436 [Application Number 13/620,116] was granted by the patent office on 2016-10-04 for linear led optical assembly for emitting collimated light.
This patent grant is currently assigned to Whelen Engineering Company, Inc.. The grantee listed for this patent is Todd J. Smith. Invention is credited to Todd J. Smith.
United States Patent |
9,459,436 |
Smith |
October 4, 2016 |
Linear LED optical assembly for emitting collimated light
Abstract
An LED optical assembly includes a linear array of LEDs,
longitudinal reflecting surfaces along each side of the array and
medial reflecting surfaces between the LEDs. The medial reflecting
surfaces are configured to redirect light oriented along the linear
array into directions that will contribute to a light emission
pattern from a warning, signaling or illumination light employing
the LED optical assembly. The medial reflecting surfaces cooperate
with other reflectors and/or lenses to integrate the redirected
light into an intended light emission pattern.
Inventors: |
Smith; Todd J. (Deep River,
CT) |
Applicant: |
Name |
City |
State |
Country |
Type |
Smith; Todd J. |
Deep River |
CT |
US |
|
|
Assignee: |
Whelen Engineering Company,
Inc. (Chester, CT)
|
Family
ID: |
50263146 |
Appl.
No.: |
13/620,116 |
Filed: |
September 14, 2012 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20140078732 A1 |
Mar 20, 2014 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B
19/0066 (20130101); F21V 7/06 (20130101); F21V
5/04 (20130101); G02B 19/0028 (20130101); F21V
7/005 (20130101); F21V 7/0033 (20130101); F21Y
2103/10 (20160801); F21W 2111/00 (20130101); F21V
13/04 (20130101); F21V 7/0091 (20130101); F21Y
2115/10 (20160801); F21V 7/04 (20130101) |
Current International
Class: |
F21V
5/04 (20060101); G02B 19/00 (20060101); F21V
7/06 (20060101); F21V 7/09 (20060101); F21V
7/00 (20060101); F21V 13/04 (20060101); F21V
7/04 (20060101) |
Field of
Search: |
;362/240,241,243,245,247,297-300,341,346 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Standard Plastic Lenses for Semiconductors," Ledil Oy, Tehdaskatu
13, 24100 SALO, Finland, Examples of Products, 14 pages (Aug. 3,
2005). cited by applicant .
"OEM Module Guide," Dialight Lumidrives Ltd., 7 pages (2006). cited
by applicant .
"L2Optics Flare Lens," L2Optics Ltd., sales brochure, 2 pages
(2005). cited by applicant.
|
Primary Examiner: Mai; Anh
Assistant Examiner: Horikoshi; Steven
Attorney, Agent or Firm: Alix, Yale & Ristas, LLP
Claims
What is claimed is:
1. An LED optical assembly comprising: a plurality of light
emitting diodes (LEDs) arranged on a support, each LED having an
optical axis and a light emission pattern surrounding said optical
axis, said plurality of LEDs being arranged in a linear array with
said optical axes arranged in a first plane, and said support being
included in a second plane perpendicular to said first plane and
provided with connections to electrical power, said light emission
pattern including light divergent from said optical axis in the
longitudinal direction and in a lateral direction perpendicular to
said longitudinal direction and said first plane; a pair of
longitudinal reflecting surfaces separated by said first plane and
extending along opposite sides of said linear array, said
longitudinal reflecting surfaces defining a trough having a
substantially constant sectional configuration; a pair of medial
reflecting surfaces extending between said longitudinal reflecting
surfaces, said medial reflecting surfaces disposed on opposite
longitudinal sides of at least one said LED and configured to
redirect a portion of the light originating at said at least one
said LED and incident upon said medial reflecting surfaces into
planes perpendicular to both said first plane and said second
plane, a portion of the light redirected by said medial reflecting
surfaces being redirected by said longitudinal reflecting surfaces
into planes parallel with said first plane, wherein said medial
reflecting surfaces are external reflecting surfaces, whereby light
emitted from said at least one LED and redirected by at least one
medial reflecting surface and at least one longitudinal reflecting
surface is collimated with respect to the optical axis of said at
least one said LED, while light redirected by only said
longitudinal reflecting surfaces is partially collimated with
respect to said first plane and retains the divergence from the
optical axis in the longitudinal direction.
2. The LED optical assembly of claim 1, wherein said longitudinal
reflecting surfaces are mirror images of each other.
3. The LED optical assembly of claim 1, wherein said medial
reflecting surfaces are mirror images of each other.
4. The LED optical assembly of claim 1, comprising a longitudinal
lens extending the length of said linear array and configured to
redirect light from said plurality of LEDs into planes parallel
with said first plane.
5. The LED optical assembly of claim 4, wherein light redirected by
at least one of said medial reflecting surfaces and said
longitudinal lens is collimated with respect to the optical axis of
said at least one said LED.
6. The LED optical assembly of claim 4, wherein said longitudinal
reflecting surfaces are defined by a trough reflector having ends
configured to receive and retain respective longitudinal ends of
said longitudinal lens.
7. The LED optical assembly of claim 1, wherein said longitudinal
reflecting surfaces and said medial reflecting surfaces are defined
by parabolic curves having a focus at an area of light emission of
said at least one said LED.
8. The LED optical assembly of claim 1, wherein said LED optical
assembly is configured for use as a warning light for an emergency
vehicle.
9. The LED optical assembly of claim 8, wherein said first plane is
horizontal.
10. An LED optical assembly comprising: a plurality of light
emitting diodes (LEDs) arranged on a support, each LED having an
optical axis and a light emission pattern surrounding said optical
axis comprising narrow angle light having a range of emitted
trajectories up to about 45.degree. relative to said optical axis
and wide angle light having a range of emitted trajectories at
least about 45.degree. relative to said optical axis, said
plurality of LEDs being arranged in a linear array with said
optical axes arranged in a first plane, and said support being
included in a second plane perpendicular to said first plane and
provided with connections to electrical power, said emitted
trajectories including a first component divergent from said
optical axis in a longitudinal direction and a second component
divergent from said optical axis in a lateral direction
perpendicular to said longitudinal direction; a pair of
longitudinal reflecting surfaces separated by said first plane and
extending along opposite lateral sides of said linear array, said
longitudinal reflecting surfaces defining a trough having a
substantially constant sectional configuration and each configured
to redirect wide angle light originating at said at least one said
LED and incident upon said longitudinal reflecting surfaces into
longitudinal reflected trajectories in planes parallel to said
first plane, said longitudinal reflected trajectories retain said
first component of said emitted trajectories divergent from said
optical axis in the longitudinal direction; a pair of medial
reflecting surfaces extending between said longitudinal reflecting
surfaces, said medial reflecting surfaces disposed on opposite
longitudinal sides of at least one said LED and each configured to
redirect wide angle light originating at said at least one said LED
and incident upon said medial reflecting surface into medial
reflected trajectories in planes perpendicular to both said first
and second planes, said medial reflected trajectories retain said
second component of said emitted trajectories divergent from said
optical axis in the lateral direction; wherein a portion of said
wide angle light originating at said at least one LED passes said
medial reflecting surface and said longitudinal reflecting surface
redirects said portion of wide angle light into longitudinal
reflected trajectories that retain said first component of said
emitted trajectories divergent from said optical axis in the
longitudinal direction.
11. The LED optical assembly of claim 10, wherein said longitudinal
reflecting surfaces are mirror images of each other.
12. The LED optical assembly of claim 10, wherein said medial
reflecting surfaces are mirror images of each other.
13. The LED optical assembly of claim 10, further comprising a
longitudinal lens extending the length of said linear array
configured to redirect a portion of the wide angle light reflected
on said medial reflecting surfaces and the narrow angle light
emitted from said plurality of LEDs and not incident upon said
medial reflecting surfaces or said longitudinal reflecting surfaces
into planes parallel with said first plane.
14. The LED optical assembly of claim 13, wherein light redirected
by at least one of said medial reflecting surfaces and said
longitudinal lens is collimated with respect to the optical axis of
said at least one said LED.
15. The LED optical assembly of claim 13, wherein said longitudinal
reflecting surfaces are defined by a trough reflector having ends
configured to receive and retain respective longitudinal ends of
said longitudinal lens.
16. The LED optical assembly of claim 10, wherein said longitudinal
reflecting surfaces and said medial reflecting surfaces are defined
by parabolic curves having a focus at an area of light emission of
said at least one said LED.
17. The LED optical assembly of claim 10, wherein said LED optical
assembly is configured for use as a warning light for an emergency
vehicle.
18. The LED optical assembly of claim 17, wherein said first plane
is horizontal.
Description
BACKGROUND
The present disclosure relates generally to warning light devices,
and more particularly to optical configurations for producing
integrated directional light from a LED light sources.
While not limited thereto in its utility, the novel technology to
be described below is particularly well suited for use in
combination with light emitting diodes (LED's) and, especially, for
use in warning and signaling lights.
Commercially available LED's have characteristic spatial radiation
patterns with respect to an optical axis which passes through the
light emitting die. A common characteristic of LED radiation
patterns is that light is emitted in a pattern surrounding the
optical axis from one side of an imaginary plane containing the
light emitting die, the optical axis being oriented perpendicular
to this plane. Typically, the light generated by an LED is radiated
within a hemisphere centered on the optical axis, with a majority
of the light emitted at angles close to the optical axis of the
LED. Although the quantity of light emitted typically declines as
the angle relative to the optical axis of the LED increases, light
emitted at angles greater than approximately 45.degree. represents
a significant portion of the overall light output of the LED. The
distribution of light radiation within this hemisphere is
determined by the shape and optical properties of the lens (if any)
covering the light emitting die of the LED. Thus, LED's can be
described as "directional" light sources, since all of the light
they generate is emitted from one side of the device, with the
other side dedicated to a support which provides electrical power
to the LED and conducts heat away from the die.
When designing light sources for a particular purpose, it is
important to maximize efficiency by ensuring that substantially all
of the generated light is arranged in a pattern or field of
illumination dictated by the end use of the device into which the
light source is incorporated. The somewhat limited overall light
output of individual LEDs frequently necessitates that several
discrete devices be cooperatively employed to meet a particular
photometric requirement. Use of arrays of LEDs and their
directional emission pattern present peculiar challenges to the
designer of warning and signaling lights. Employing LEDs in compact
arrays additionally imposes cooling, i.e., "heat sinking",
requirements which were not present in the case of prior art
warning and signal light design.
SUMMARY
The present disclosure includes an optical assembly configured to
produce an integrated light emission pattern relative to a first
plane with limited spread in imaginary planes perpendicular to the
first plane. For purposes of this application, light emitted from
an LED can be described as "narrow angle" light emitted at an angle
of less than about 45.degree. from the optical axis and "wide
angle" light emitted at an angle of more than about 45.degree. from
the optical axis as shown in FIG. 11. The initial trajectory of
wide angle and narrow angle light may necessitate manipulation by
different portions of a reflector and/or optical element to provide
the desired illumination pattern.
In one disclosed embodiment, a plurality of LEDs are arranged on a
support in a linear array, with the optical axes of the LEDs
included in a first imaginary plane perpendicular to the support.
An imaginary linear focal axis extends through the dies of the
plurality of LEDs. Reflecting surfaces extend along either side of
the array, forming a concave reflective trough. The reflective
trough may be defined by a parabolic curve having a focus
coincident with the linear focal axis and projected along said axis
to form a linear parabolic surface. An elongated lens is positioned
above the LEDs and longitudinally bisected by the first imaginary
plane. The elongated lens and trough are configured so that light
may not be emitted from the optical assembly without passing
through the elongated lens or being redirected by the trough
reflector. The elongated lens is configured to redirect light
emitted from the array of LEDs (and not incident upon the
reflecting trough) from its emitted trajectory into imaginary
planes parallel with the first plane. The reflective trough
redirects wide angle light (light not passing through the elongated
lens) from its emitted trajectory into imaginary planes parallel
with the first plane. The redirection performed by the trough
reflector and elongated lens may be described as "partially
collimated" or "collimated with respect to the first plane." Such
partially collimated light retains the component of its emitted
trajectory within the imaginary planes into which it is redirected,
whereas fully collimated light is parallel with a line such as the
optical axis of an LED.
In the disclosed embodiments, medial reflecting surfaces are also
positioned between adjacent pairs of LEDs, to redirect a portion of
the wide angle light from each LED into imaginary planes
perpendicular to the first imaginary plane containing the optical
axes of the LEDs. This subset of wide angle light from each LED is
partially collimated with respect to an imaginary plane
perpendicular to the first plane and including the optical axis of
the respective LED. Light reflected from the medial reflecting
surfaces retains the component of its emitted trajectory within the
imaginary planes into which it is redirected, however this light
must be further redirected by the elongated lens or trough
reflector before being emitted from the optical assembly, where it
is redirected into planes parallel with the first plane. Thus, the
subset of wide angle light incident upon the medial reflectors is
fully collimated with respect to the respective optical LED optical
axis before exiting the optical assembly.
The shape of the medial reflecting surfaces is dictated by their
function, e.g., redirecting this subset of wide angle light into
trajectories having a smaller angular component with respect to
imaginary planes perpendicular to both the first plane (containing
the optical axes of the LEDs) and a plane defined by the LED
support. The medial reflecting surfaces may take many forms, but
preferably comprise a convex surface when viewed from a direction
toward the LED support. A preferred surface configuration for the
medial reflecting surface partially collimates the subset of wide
angle light incident upon the medial reflecting surfaces into
imaginary planes substantially perpendicular to both the first
plane containing the LED optical axes and a plane defined by the
LED support. In the disclosed embodiments, the medial reflecting
surfaces are defined by a parabola having a focus centered on the
area of light emission of a respective LED. This parabolic curve is
then rotated about the imaginary linear focal axis of the array to
form a three dimensional surface. The medial reflecting surfaces on
either side of a respective LED are mirror images of each other.
Other surface configurations approximating the intended function of
the disclosed medial reflecting surfaces will occur to those
skilled in the art. A semi-conical surface is an example of such an
alternative configuration.
In the absence of the medial reflecting surfaces, the subset of
wide angle light redirected by the medial reflecting surfaces would
continue on its emitted trajectory and be lost (absorbed or
scattered) within the assembly or be partially collimated by the
trough reflector and elongated lens (into imaginary planes parallel
with the first plane containing the LED optical axes). In either
case, the retained component of the emitted trajectory of this
subset of wide angle light (within the imaginary planes) means it
cannot contribute to a majority of desirable light emission
patterns and is effectively wasted.
It is known in the field of optics that reflecting surfaces may be
formed as an internal reflecting surface or as polished or
metalized external surfaces. Both types of surfaces are disclosed
herein and are intended to be encompassed in the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring to the drawings, wherein like numerals refer to like
elements in the several Figures:
FIG. 1 is a front perspective view of a warning signal light
including an LED optical assembly according to a first embodiment
of the disclosure;
FIG. 2 shows the warning signal light and LED optical assembly of
FIG. 1 with the longitudinal lens of the optical assembly removed
for clarity;
FIG. 3 is front perspective view of the reflector of the optical
assembly of FIG. 1;
FIG. 4 is a rear perspective view of the longitudinal lens of the
optical assembly of FIG. 1;
FIG. 5 is a side plan view of the longitudinal lens of FIG. 4;
FIG. 6 is an enlarged end view of the longitudinal lens of FIGS. 4
and 5;
FIG. 7 is an enlarged sectional view through an LED optical
assembly according to aspects of the disclosure;
FIG. 8 is an enlarged partial front perspective view of an LED
optical assembly according to aspects of the disclosure;
FIG. 9 is a partial longitudinal sectional view through the LED
optical assembly of FIG. 8;
FIG. 10 is a partial perspective view from above of the LED optical
assembly of FIG. 8;
FIG. 11 is an enlarged top plan view of the LED optical assembly of
FIG. 8;
FIG. 12 is a front elevation view of a second embodiment of an LED
optical assembly according to aspects of the disclosure;
FIG. 13 is a longitudinal section view of the LED optical assembly
of FIG. 12;
FIG. 14 is cross sectional view of an LED optical assembly
consistent with the LED optical assemblies of FIGS. 12 and 13;
FIG. 14A is a three dimensional rendering of an optical element of
the LED optical assembly of FIGS. 12-14;
FIG. 15 is an enlarged, partial longitudinal sectional view of the
LED optical assembly of FIGS. 12-14;
FIG. 16 is an enlarged, partial front view of the LED optical
assembly of FIGS. 12-14; and
FIG. 17 is an enlarged partial longitudinal sectional view of the
LED optical assembly of FIGS. 12-14.
DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS
LED optical assemblies according to aspects of the present
disclosure will now be described with reference to the figures, in
which common reference numerals are used to designate similar
components. FIGS. 1-11 illustrate a first LED optical assembly
according to aspects of the disclosure. FIGS. 12-17 illustrate a
second embodiment of an LED optical assembly according to aspects
of the disclosure. The disclosed LED optical assemblies are
suitable for use in emergency vehicle warning lights, but the
disclosed optical assemblies may be appropriate for use in other
warning and signaling apparatus as well as general illumination
applications.
As shown in FIGS. 1-6, a warning light 20 incorporates an LED
optical assembly 10 which includes a reflector 12, a longitudinal
lens 14, medial reflecting surfaces 40 and LED light sources 18.
The LED light sources 18 are arranged in a linear array on a planar
support, such as a PC board 22. As shown in Figure ach LED 18 has
an optical axis O.sub.A originating at the light emitting die of
the LED 18 and projecting perpendicular to a plane P defined by the
PC board 22 or other LED support. The LEDs 18 are arranged in a row
with an imaginary linear focal axis F.sub.A extending through the
light generating dies of the LEDs 18. The optical axes O.sub.A of
the row of LEDs are contained in a common plane P.sub.1
perpendicular to a plane P defined by the LED support (PC board
22). A longitudinal lens 14 is positioned above the row of LEDs 18
and extends the length of the reflector 12. In the disclosed
embodiments, the lens 14 has a substantially constant sectional
configuration and is designed to redirect light originating at the
LEDs 18 and passing through the lens 14 into imaginary planes
parallel with the plane P.sub.1 containing the LED optical axes
O.sub.A. Light passing through the lens 14 will retain the
component of its trajectory (if any) that is not parallel with
plane P.sub.1 and according to the terminology used in this
application is "partially collimated" with respect to plane
P.sub.1. The sectional configuration of the disclosed longitudinal
lens 14 is a conventional double convex configuration with modified
longitudinal edges 15 to permit light to pass the lens 14. Other
lens configurations will occur to those skilled in the art which
will accomplish the function of partially collimating light from
the LEDs and are compatible with the present disclosure.
The reflector 12 in the disclosed embodiments includes parallel,
mirror image reflecting surfaces extending along each side of the
array of LEDs 18. The function of the reflector is to redirect
light originating from the LEDs 18 into planes parallel with plane
P.sub.1 which includes the optical axes O.sub.A of the LEDs 18.
Light originating from the LEDs 18 and redirected by the reflector
will retain the component of its trajectory (if any) that is not
parallel with plane P.sub.1 and thus may be described as partially
collimated with respect to plane P.sub.1. The disclosed
configuration of the reflector 12 is a linear parabolic surface
having a focus at the imaginary linear focal axis F.sub.A of the
array of LEDs. Other surface configurations will occur to those
skilled in the art that will approximate this functionality and are
intended to fall within the scope of the disclosure.
As best seen in FIGS. 1-6, the reflector 12 and lens 14 are
configured to snap together, with the ends of the reflector
retaining the ends of the longitudinal lens 14. With reference to
FIG. 3, the ends of the reflector include openings 24 between a
cradle 26 and a retention tab 28. As shown in FIGS. 4-6, ends 30 of
the longitudinal lens have a configuration complementary to the
cradle 26 and tab 28. One end of the lens 14 is inserted into an
opening 24 and advanced through the opening against the resilient
movement of the tab 28. When one end 30 of the lens 14 has moved
through the opening 24 sufficiently to permit the opposite end 30
to enter the reflector, the lens is pushed into the reflector until
the end bears on the tab at the opposite end, which flexes to
permit the lens ends 30 to be seated in their respective cradles 26
and held in place by the tabs. The disclosed lens 14 also includes
a fastener receptacle, which also functions as a stand off to
maintain the central portion of the length of the longitudinal lens
14 in position above the array of LEDs 18. Securing the lens 14 at
both ends and in the middle helps prevent the lens from bowing away
from the intended straight position under the influence of changing
environmental conditions (temperature). In the disclosed warning
lights 20, fasteners 21 extend through a heat sink 23 (see FIG. 2)
and the PC board 22 to pull the reflector 12 and lens into an
installed position and maintain an efficient thermal contact
between the PC board 22 and the heat sink.
FIGS. 2, 3, and 8-11 illustrate a disclosed configuration for
medial reflecting surfaces 40 positioned between the reflecting
surfaces 12a and 12b. As shown in FIG. 2, the linear array of LEDs
extends between the reflecting surfaces 12a, 12b of the reflector
12. Each LED 18 emits light in a hemisphere surrounding its
respective optical axis O.sub.A. Those skilled in the art will
recognize that the emitted trajectory of some of the light from
LEDs in the array will not reinforce a desirable light emission
pattern for the warning light 20 and is effectively wasted. In the
disclosed warning light configuration, the light least likely to
end up where it is useful is light emitted in a cone best
understood with reference to FIGS. 9 and 11. The potentially wasted
light is wide angle light emitted from each LED in a cone
originating at the area of light emission (the LED die) and having
a cone axis coincident with the linear focal axis F.sub.A of the
LED array, so there are two such cones of light for each LED in the
array. As best seen in FIG. 9, light incident upon the medial
reflecting surfaces is emitted from the respective LED at an angle
A of at least 45.degree. relative to the optical axis O.sub.A of
the LED. Angle B in FIG. 9 is the difference between angle A and
90.degree., and in the disclosed embodiments is approximately
40.degree.. As best seen in FIG. 11, the medial reflecting surfaces
extend between the linear reflecting surfaces 12a, 12b of the
trough reflector to redirect light having an emitted trajectory of
less than approximately 40.degree. from the linear focal axis
F.sub.A of the LED array and at an emitted trajectory of greater
than approximately 45.degree. relative to the optical axis O.sub.A
of each respective LED 18. The result is redirection of a cone of
light, where the cone has a radius equal to half the lateral
distance between the linear reflecting surfaces 12a, 12b, an
included angle C of approximately 80.degree. and a height (measured
along the linear focal axis F.sub.A) of half the distance between
LEDs in the array. It will be apparent that the cone of light is
half a cone above the plane P defined by the LED support.
The medial reflectors are configured to redirect this light into
trajectories that will contribute to the overall light emission
pattern of the warning light 20. Generally speaking, such
redirected trajectories are those closer to the optical axis
O.sub.A of the respective LED 18 and/or further from the linear
focal axis F.sub.A of the linear array. One disclosed configuration
for the medial reflecting surface is defined by a parabolic curve
having a focus at the area of LED light emission and rotated about
the linear focal axis F.sub.A. This surface shape is best observed
in the three dimensional renderings of FIGS. 8 and 10. As shown in
FIGS. 9 and 11, light incident upon the medial reflecting surfaces
40 is redirected into planes P.sub.2 perpendicular to both the
support plane P and the plane P.sub.1 containing the optical axes
O.sub.A of the LEDs 18. As shown in FIGS. 8 and 10, light incident
upon the medial reflecting surfaces 40 retains the component of its
emitted trajectory within the planes P.sub.2 until passing through
the longitudinal lens 14 or being reflected by the trough
reflecting surfaces 12a, 12b. Light that is first redirected by the
medial reflecting surfaces and then by the longitudinal lens 14 or
trough reflecting surfaces is fully collimated (parallel) with
respect to the optical axis of the respective LED 18, as shown in
FIGS. 8 and 10. Thus light incident upon the medial reflecting
surfaces 40 is incorporated into a desirable light emission pattern
for the warning light 20.
It will be observed that in the warning light embodiment of FIGS.
1-11, LED light that is not incident upon the medial reflecting
surfaces 40 is not fully collimated with respect to the optical
axis O.sub.A of the respective LEDs and retains the component of
its emitted trajectory (if any) within planes parallel with plane
P.sub.1 containing the optical axes O.sub.A of the LED array. The
retained component of the emitted trajectory gives the warning
light depicted in FIGS. 1-11 a wide angle light emission pattern
which is ideal for many warning and signaling applications. The
light emission pattern may be altered by employing the trough
reflector 12 in combination with the medial reflecting surfaces,
but omitting the longitudinal lens 14. Such an optical assembly
would produce a light emission pattern having enhanced vertical
spread, since the collimating action of the longitudinal lens 14
would be eliminated and light not incident upon either the trough
reflecting surfaces 12a, 12b or the medial reflecting surfaces 40
would retain both components of its emitted trajectory. Such an
optical configuration would partially collimate wide angle light
incident upon the trough 12 and medial reflecting surfaces 40, but
would permit narrow angle light to exit the assembly without
redirection.
FIGS. 12-17 illustrate an alternative LED optical assembly
according to aspects of the disclosure. The trough reflector 12 and
longitudinal lens 14 are configured and operate in the same manner
as that described with respect to the embodiment of the LED optical
assembly illustrated in FIGS. 1-11. The LEDs 18 employed in both
embodiments have the same operational characteristics.
Those skilled in the art will recognize that a reflecting surface
may be an external, polished or metalized surface or may be an
internal surface of an optical solid, or so-called internal
reflecting surface. In the embodiments shown in FIGS. 12-17, the
medial reflecting surfaces are created as internal reflecting
surfaces 50 of a three dimensional optical solid. As shown in FIGS.
12 and 13, each LED 18 is covered by a specifically configured
optic that provides internal reflecting surfaces 50 arranged to
redirect light in the same manner as the medial reflecting surfaces
40 described with respect to the LED optical assembly embodiment
shown in FIGS. 1-11. As can be seen in FIG. 14, the basic structure
of the LED optical assembly is the same as the previously described
embodiment. An LED support defines a plane P and an LED optical
axis O.sub.A projects from the LED area of light emission and
perpendicular to the plane P. A solid optical segment 52 is
constructed to partially collimate all the light from a respective
LED with respect to planes P.sub.2 that are perpendicular to both
the support plane P and the plane P.sub.1 containing the optical
axes of the linear array of LEDs 18.
The optical segment is best described with reference to 13 and 14A.
The optical segment 52 is defined by the sectional shape shown in
FIG. 13 rotated approximately 180.degree. about axis of revolution
A.sub.R. Thus, the illustrated surfaces 50, 54, and 56 become
surfaces of revolution centered on the axis of revolution A.sub.R.
Each optical segment 52 includes a plurality of surfaces, with
three groups of surfaces each performing a different optical
function. Generally speaking, each optical segment 52 includes
light entry surfaces 60, 62, light emission surfaces 54, 56 and an
internal reflecting surface 50. More specifically, the light entry
surface of each optical segment 52 includes a pair of light entry
portions 60, 62 that together define a cavity 58. Light entry
portions 60, 62 are arranged to intercept substantially all of the
light rays comprising the light flux emitted by an associated LED
18. Finally, each optical element 52 has an internal reflecting
surface 50. As may best be seen from FIGS. 13-17, internal
reflecting surface is actually comprised of a pair of surfaces 50
which are mirror images and which are oppositely disposed with
respect to an associated cavity 58. Similarly, the light entry
surface 62 is actually defined by a pair of surfaces which are
mirror images and which define two opposite sides of a cavity
58.
As shown in FIG. 17, the light entry surfaces 60, 62 and the
internal reflecting surfaces 50, through respective cooperative
refraction and internal reflection, redirect the wide angle light
from a respective LED 18 such that they are emitted from each
optical element 52 as partially collimated light in planes P.sub.2
perpendicular to both the support plane P and the plane P.sub.1
containing the LED optical axes O.sub.A. The shape of each of the
internal reflecting surfaces 50 is configured for cooperation with
a corresponding light entry surface 62. Light redirected by
internal reflecting surfaces 50 is emitted from the optical segment
52 via respective emission surfaces 54 in planes P.sub.2.
Light entry surface 60 cooperates with light emission surface 56 to
partially collimate light not redirected by surfaces 62 and 50.
Thus, substantially all the light from LED 18 is partially
collimated into planes P.sub.2. As shown in FIG. 16, light emitted
from optical segments 52 retains the component of its emitted
trajectory within planes P.sub.2 until it is redirected by the
reflecting surfaces 12a, 12b or longitudinal lens 14. The resulting
light emission from the LED optical assembly of FIGS. 12-17 is
fully collimated. The LED optical assembly of FIGS. 12-17 may be
more suitable for a directional light or application calling for a
collimated light emission pattern. Omission of the longitudinal
lens 14 from the LED optical assembly of FIGS. 12-17 results in a
light emission pattern having enhanced spread or divergence with
respect to plane P.sub.1 containing the optical axes O.sub.A of the
array of LEDs 18.
While exemplary embodiments have been set forth for purposes of
illustration, the foregoing description is by way of illustration
and not limitation. Accordingly, various modifications, adaptations
and further alternatives may occur to one of skill in the art
without the exercise of invention.
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